1. Field of the Invention
The present invention relates to a clutch apparatus for a power unit having an internal combustion engine, and to a power unit including the clutch apparatus. More particularly, the present invention relates to a clutch apparatus having a clutch outer member, a clutch inner member, and a pressure plate with a communicating portion formed therein to discharge oil from a recessed portion of the pressure plate towards friction and clutch discs supported by the clutch outer member and clutch inner member, respectively.
2. Description of the Background Art
In a wet type multi-plate clutch apparatus for a power unit having an internal combustion engine, oil is raised by the rotation of a clutch outer member to thereby lubricate and cool the clutch apparatus. In general, the oil is stored in a lower portion of a power unit case in a rest condition of the internal combustion engine, and a lower portion of the clutch outer member is immersed in the oil thus stored in the lower portion of the power unit.
When the internal combustion engine is started to increase its rotational speed, the oil stored in the power unit case is fed to portions to be lubricated and cooled by an oil pump resulting into the oil level in the power unit case being lowered. Further, the oil is scattered toward the outer circumference of the clutch outer member by a centrifugal force due to the rotation of the clutch outer member thereby the amount of oil to be supplied to the clutch apparatus becomes insufficient. In order to cope with this problem, the oil atomized or splashed in the power unit case by the rotation of the clutch outer member is caught on the inner surface of a clutch cover, and thereafter is guided into the clutch apparatus.
A wet type multi-plate clutch apparatus for a power unit having an internal combustion engine mounted on a motorcycle or the like is shown in the Japanese Patent Laid-open No. Hei 10-274256 (FIGS. 2 and 3). The wet type multi-plate clutch apparatus according to the Japanese Patent Laid-open No. Hei 10-274256 includes a structure in which a pressure plate is formed with an oil-introducing hole for introducing the oil for lubrication and cooling into the clutch apparatus.
In the clutch apparatus shown in the Japanese Patent Laid-open No. Hei 10-274256, the pressure plate is formed with a plurality of deep recesses for respectively mounting a plurality of coil springs (clutch springs), and the oil-introducing hole is formed between the deep recesses. Further, a rib for guiding the oil is connected to a portion of the pressure plate having the oil-introducing hole, thereby guiding the oil raised by the clutch outer member into the clutch apparatus.
However, when the oil is introduced from the oil-introducing hole to the inside of the pressure plate in the clutch apparatus shown in the Japanese Patent Laid-open No. Hei 10-274256, the oil enters the deep recesses of the pressure plate and stays therein by the centrifugal force of the pressure plate. It is difficult to discharge this oil from the deep recesses.
The present invention has been made to overcome such drawbacks of the existing clutch apparatus. Accordingly, it is one of the objects of the present invention to provide a clutch apparatus which can easily discharge the oil from the deep recesses formed in the pressure plate to thereby improve the ability to lubricate and cool the friction discs and the clutch discs near the deep recesses.